Ensuring accuracy in optical and electrical measurement of ultra-bright LEDs during reliability test

In order to accurately estimate the lifetime of Light Emitting Diodes (LEDs), accelerated stress tests have to be performed, and measurements done throughout the tests should be free of artifact and repeatable to ensure accurate observations of the degradation of the LEDs. In this work, measurements artifact arising from DC biasing and PWM settings were first presented. Electrical measurements consistency was then studied. Optimized setting for accurate measurement is obtained using Response Surface Method with Central Composite Design, and the setting is verified through experiments.

► We studied the effects of sourcing on the accuracy of electrical and optical measurements LEDs.
► DC sourcing is found to cause lumen degradation over measuring time.
► Duty cycle above 4% cause a drop in forward voltage measured with increasing pulse width.
► Response Surface Method used to find effects of pulse width and duty cycle on optical measurements.
► Optimized setting of 30 ms pulse width and 4% duty cycle obtained from the response surface.